The customized telephone numbers of mobile unit are the numbers either defined by the users or the government(s). Unlike the ordinary telephone numbers, these customized telephone numbers are portable to certain degree or can be recognized in more than one routing area. The users of mobile unit can use these customized telephone numbers to make a direct call.
A scenario of the customized telephone number defined by the government is the 9-1-1 emergency number in United States and Canada. However, 1-1-9 is the emergency call number in Taiwan; 1-1-2 is the single emergency telephone number for the European Union; 0-0-0 and 1-1-2 for Australia; in Belgium, besides 1-1-2, one can dial 1-0-0 and 1-0-1. Having various emergency numbers in various countries can be problematic. For example, dialing 9-1-1 and asking emergency service in Australia or European Union (EU) will not work. Since the customized telephone numbers are not uniform throughout the world, it is a problem for users to use a consolidated single telephone number to deal with the emergency calls globally. Therefore, there is a need to have a single emergency telephone number that can be used around the world.
Regarding the customized telephone number defined by the users, each user has her/his personal reference number. The users may define a customized telephone number for a bank or library that they are familiar with. However, a bank or a library may have more than one branch in different cities. When a user is traveling in different cities, she/he should write down the telephone numbers of branches in their phone book and needs time to look for it. It is desirable to have a single customized phone number for “Bank” during traveling in different cities to connect to the local branch.
A solution to this problem was proposed by Menard et al, U.S. Pat. No. 5,719,929. However, the prior art requires apparatus at both the mobile unit and the mobile network side. If the network doesn't provide the features proposed in U.S. Pat. No. 5,719,929, the users cannot use the single calling number approach to simplify the dialing process.